1. Field of the Invention
The present invention relates to a novel visible light photosensitizer of thiobarbituric acid series for a photopolymerizable or a photocrosslinkable composition having an excellent thermal stability, a photopolymerizable and/or a photocrosslinkable composition containing a thiobarbituric acid derivative (a coloring matter) and having excellent characteristics which can be sensitized by the thiobarbituric acid derivative compounds, and a hologram recording medium having an excellent reproducibility which is obtained by using the photosensitive composition.
2. Related Background Art
The present inventors have intensively conducted investigations into a sensitizer for a photopolymerizing initiator or a photocrosslinking agent which has excellent photosensitizing properties and in which an absorption maximum is shifted to a long wavelength by elongating or fixing a conjugated double bond of a coumarine derivative and a pyran derivative represented by the following formulae (Japanese Patent Application Nos. 5-144423 and 5-132482). ##STR2##
The absorption maximum of each of the abovementioned compounds can be shifted to a long wavelength by elongating its conjugated double bond, and these compounds can sensitize polymerizing initiators and crosslinking agents such as diarylhalonium salts, halomethyl-s-triazines, halogen compounds, bisimidazole derivatives and organic peroxides. Therefore, the above-mentioned compounds can be used as a material for the formation of photosensitive compositions and photosensitive resin compositions.
Since the absorption maximum could be shifted to the long wavelength by the synthesis of a compound in which the conjugated double bond was elongated, it was possible to adjust an absorption maximum in a green region, but it had not been accomplished yet to synthesize a coloring matter with high sensitivity in a red region.
It has been heretofore reported that a thiobarbituric acid derivative, a coloring matter, was used as an analytical reagent for the detection of gold, silver or the like, but this coloring matter has not been used as a sensitizing agent, and it has not also been investigated to shift a sensitizing region to a long wavelength by elongating the conjugated double bond. However, according to the detailed investigation by the present inventors, it is apparent that when the conjugated double bonds are introduced into the thiobarbituric acid derivative having an absorption sensitivity in the red region which can be used as the photosensitizer for the photopolymerizing initiator and/or the photocrosslinking agent, the high-sensitive coloring matter can be obtained which is particularly useful in the red region (Japanese Patent Application No. 6-87271).
On the other hand, various kinds of the sensitizing agents having the sensitivity in the red region are known, but a higher sensitivity, the improvement of fading properties by light irradiation and the like have been desired for the sake of the preparation of a hologram having an excellent transparency. In order to improve the transparency of the hologram, it is important that the sensitizing agent can easily be removed by a solvent or the like as one of the characteristics of the sensitizing agent, but if the sensitizing agent is excellent in photofading properties, a step of removing the sensitizing agent by a solvent can be omitted. Therefore, it is more important from the viewpoint of the simplification of the manufacturing process of the hologram that the sensitizing agent is excellent in photofading properties.
Heretofore, various kinds of hologram recording media have been reported, but their sensitivity is much lower as compared with that of a bleached silver salt hologram sensitive material, and therefore it has been desired to develop a photopolymeric hologram recording medium having a higher sensitivity.
On the contrary, the coloring matter of thiobarbituric acid derivatives which has been suggested by the above-mentioned present inventors is excellent in photoreactivity and particularly photofading properties, and so this coloring matter is useful as a material for forming the hologram recording medium, but it has the following two drawbacks:
(1) Its solubility in an organic solvent is low.
(2) Its thermal stability is poor as a photosensitive solution (a dark reaction easily proceeds).